Mazus jiangshiense Y.B. Chen, Xin Y. Chen & Liang Ma, 2024

Chen, Yong-Bin, Chen, Xin-Yan, Ma, Liang, Zhao, Zhuang & Chen, Shi-Pin, 2024, Mazus jiangshiense (Mazaceae), a new species from China: evidence from morphological and molecular analyses, PhytoKeys 241, pp. 81-90 : 81

Mazus jiangshiense Y.B. Chen, Xin Y. Chen & Liang Ma sp. nov.

Type.

China. Fujian Province, Shaowu County, 27°03'46"N, 117°15'40"E, elev. ca. 395 m, July 2022, Y.B. Chen et al. 20220801015 (holotype: FJFC, POC592371!; isotype: CSH, POC592372!) (Figs 2 , 3 )

Diagnosis.

Results of morphological observation suggest that the newly-identified Mazus is similar to M. gracilis Hemsl. ex Forbes & Hemsl. ( Forbes and Hemsley 1890) and M. procumbens Hemsl. ex Forbes & Hemsley ( Forbes and Hemsley 1890), but it differs in the stem texture and whether the ovary is villous or not. It is also close to M. spicatus Vaniot ( Vaniot 1905), but it can be easily distinguished by the growth habit of the stem and texture. Table 2 displays a detailed comparison of morphological characteristics.

Description.

Perennials, densely villous. Stems creeping to 50 cm, soft, slender, branched, base woody, inter-node nearly 5 cm, often longer than or equal to leaves, nodal rooting. Basal leaves are several to numerous, often deciduous. Cauline leaves opposite or alternate, leaf blade subrounded or oblong, membranous, 2.5-5.5 cm long including petiole, 2.1-4.1 cm width, larger at base of the stem, adaxially green, abaxially greyish-green to silver grey, apex acute to obtuse, base truncate and tapering, margin coarsely crenate, both sides villous; lateral veins 3-4 pairs, fluted adaxially, elevated abaxially and conspicuous on both surfaces; petiole 0.5-2.5 cm, slender, villous. Racemes axillary or terminal, obliquely ascending, to 17.0 cm or more, villous, sparse, multiflowered to 20; pedicels slender, 0.6 cm in fruit, densely villous; Calyx funnelform, 3.0-4.0 mm, slightly enlarged in fruit, villous on both surfaces, lobes 5, lanceolate, acute and longer than the tube. Corolla light purple or white, 0.9-1.1 cm long, dotted yellow on the palate and with sparse glandular-hair, tube cylindrical with glandular-hair, 0.4-0.5 cm long; limb 2-lipped, upper lip bilobed, lobes lanceolate, apex acute, slightly upturned; lower lip trilobed, middle lobe oblong, smaller and narrower than lateral lobes, lateral lobes broadly ovate, spreading away from middle lobes; plaits with sparse glandular hairs; palate comprising 2 longitudinal elevations, mostly hidden in the corolla tube, covered by sparse glandular hairs, clavate hairs, white to transparent, 0.6 mm long. Stamens 4, filaments protruding from the tube, appressed to the corolla tube, glabrous, included, anterior pair longer, curved, anthers positioned adjacent to the corolla tube on upper lip; Ovary villous, styles ca. 0.5 cm long, stigma lamellate, included. Capsule oblong, ca. 2.5 mm long, ca. 1.5 mm diam., apex rounded and villous. Seeds brown-yellow, numerous.

Chinese vernacular name.

jiāng-shí-tōng-qúan-căo (将石通泉草).

Phenology.

The flowering period is from June to July and the fruiting period is from August to September.

Etymology.

The new species was named after the locality of Jiangshi Provincial Nature Reserve, where it was discovered.

Distribution and habitat.

The species is distributed in Xiao Jiafang Town of Shaowu County, northwest Fujian Province, China and grows under a stone cave in a cliff at an elevation of approximately 395 m (Fig. 2A ).

Phylogenetic analysis.

The nucleotide sequence lengths for the new species nrITS, plastid rps16, rbcL and trnL-trnF are 550 bp, 806 bp, 1261 bp and 930 bp, respectively. Table 3 provides a summary of the characteristics of each dataset utilised in this study. The phylogenetic analyses are presented in the form of Maximum Likelihood (ML) trees and the support values, including bootstrap percentages (BSML/BSMP) and posterior probabilities (PP), are indicated near the respective nodes. Upon analysis of the combined dataset, the phylogenetic trees consistently demonstrated that the new species is closely related to M. spicatus , garnering robust support (BPML = 78, PP = 0.99, BPMP = 68). The tree derived from the nrITS dataset (Fig. 1A ) corroborates this relationship, with strong support for the new species being the sister to M. spicatus (BPML = 82, PP = 0.99, BPMP = 75). However, the plastid-based phylogenetic tree introduces an intriguing twist, indicating that the new Mazus species is proximate to M. caducifer Hance ( Hance 1882), M. spicatus and M. humilis Hand-Mazz ( Hong et al. 1998). This forms a collapsed topology (Fig. 1B ), suggesting a potentially intricate evolutionary relationship amongst these species.

Conservation status. Following our comprehensive biodiversity survey of Shaowu Jiangshi Provincial Nature Reserve in July 2022, more than 500 individuals of Mazus jiangshiense have been identified in three distinct locations within the Reserve; the three populations are considerably distant from each other and collectively occupy an area of approximately 100 m2. Fruiting individuals were observed in each population. Given the management efforts of the Provincial Nature Reserve, it is currently at low risk of existential threats.

Figures

Figure 1. The phylogenetic tree was constructed by the plastid, ITS and combined matrix using Maximum Likelihood, Maximum Parsimony and Bayesian Inference methods. The numbers near the nodes are bootstrap percentages and Bayesian posterior probabilities (BPML, PP, BPMP). Separate combined results of nrITS (A) and plastid (B) are shown in the top left corner. A dash (-) indicates that the node is inconsistent between the Bayesian tree and the topology of the MP / ML trees. The asterisk (*) node is 1.00 posterior probability or 100 bootstrap percentage.

Figure 2. Morphology of Mazus jiangshiense A, B habitat C flowering plant D roots and stolons E leaves F inflorescence G a mature inflorescence with flowers and fruits H corolla I pedicel, calyx, stamens and pistils J fruit K seed.

Figure 3. Mazus jiangshiense Y. B. Chen, Xin Y. Chen & Liang Ma A plant B leaves C-E corolla F stamens G pistils H calyx I seed.